Sebastian thought it was the right thing to get them together for a little trip after the rift on their family that was guilty enough, because of him. He can also see it as an opportunity to settle things with Freyr, after all they cannot see eye to eye from that last conversation that frightened him.
Okay, he knew he was in the wrong and Freyr was only preventing a serious nightmare that no brother would like to set their mind and foot to. Even if he's as frightened to Freyr he respects that foot forward to restrain his feelings which is..kind of working.